Model 3.—6-cylinder. 50-60 h. p., weight 210 pounds.
Model 4.—6-cylinder, 60-75 h. p., weight 275 pounds.
This motor is of the 4-cycle, vertical, water-cooled type. Roberts Aviation Motor.
One of the successful aviation motors of American make, is that produced by the Roberts Motor Co., of Sandusky, Ohio. It is designed by E. W. Roberts, M. E., who was formerly chief assistant and designer for Sir Hiram Maxim, when the latter was making his celebrated aeronautical experiments in England in 1894-95. This motor is made in both the 4- and 6-cylinder forms. The 4-cylinder motor weighs complete with Bosch magneto and carbureter 165 pounds, and will develop 40 actual brake h. p. at 1,000 r. p. m., 46 h. p. at 1,200 and 52 h. p. at 1,400. The 6-cylinder weighs 220 pounds and will develop 60 actual brake h. p. at 1,000 r. p. m., 69 h. p. at 1,200 and 78 h. p. at 1,500.
Extreme lightness has been secured by doing away with all superfluous parts, rather than by a shaving down of materials to a dangerous thinness. For example, there is neither an intake or exhaust manifold on the motor. The distributing valve forms a part of the crankcase as does the water intake, and the gear pump. Magnalium takes the place of aluminum in the crankcase, because it is not only lighter but stronger and can be cast very thin. The crankshaft is 2 1/2-inch diameter with a 2 1/4-inch hole, and while it would be strong enough in ordinary 40 per cent carbon steel it is made of steel twice the strength of that customarily employed. Similar care has been exercised on other parts and the result is a motor weighing 4 pounds per h. p.
The Rinek Motor.
The Rinek aviation motor, constructed by the Rinek Aero Mfg. Co., of Easton, Pa., is another that is meeting with favor among aviators. Type B-8 is an 8-cylinder motor, the cylinders being set at right angles, on a V-shaped crank case. It is water cooled, develops 50-60 h. p., the minimum at 1,220 r. p. m., and weighs 280 pounds with all accessories. Type B-4, a 4-cylinder motor, develops 30 h. p. at 1,800 r. p. m., and weighs 130 pounds complete. The cylinders in both motors are made of cast iron with copper water jackets.
The Overhead Camshaft Boulevard.
The overhead camshaft Boulevard is still another form of aviation motor which has been favorably received. This is the product of the Boulevard Engine Co., of St. Louis. It is made with 4 and 8 cylinders. The former develops 30-35 h. p. at 1,200 r. p. m., and weighs 130 pounds. The 8-cylinder motor gives 60-70 h. p. at 1,200 r. p. m., and weighs 200 pounds. Simplicity of construction is the main feature of this motor, especially in the manipulation of the valves.